To direct-post to Instagram, the first thing you should take into account is that you need an Instagram Business account that's connected to a Facebook page. Those are Instagram requirements. You can also schedule posts to Personal accounts, but you'll need to push them through a notification sent to your phone.
Now that being said, scheduling to Instagram is quite easy. First, make sure you connect your accounts to Postcron. Once you're all set, select the accounts you'll be posting to on the upper part of the screen. Then, click on the Composer to open it and create your post. Make sure you attach either a video or photo, as Instagram is an image-oriented social network.
After you upload a media file, schedule your posts using the available options: Schedule, to manually pick the date and time, Predefined Times, or Post Now*. And that's it!
If your video is 15 seconds or less, you'll notice a Story or Reel switch set to Reel. If you want to post a Story, you can change your post type here. Keep in mind that stories can be automatically posted only on Instagram Business accounts.
*Keep in mind that Post Now is a Premium feature on Postcron.